This invention relates to the treatment of a subterranean formation in order to increase its permeability and, more particularly, to a hydraulic fracturing treatment of the formation with oxygenated foam as the fracturing fluid followed by in-situ combustion between the oxygenated foam and hydrocarbons with the formation.
It is oftentimes desirable to treat subterranean formations in order to increase the permeability thereof. For example, in the oil industry, it is conventional to hydraulically fracture a well in order to produce one or more fractures in the surrounding formation and thus facilitate the flow of oil and/or gas into the well or the injection of fluids such as gas or water from the well into the formation. Such hydraulic fracturing is accomplished by disposing a suitable fracturing fluid within the well opposite the formation to be treated. Thereafter, sufficient pressure is applied to the fracturing fluid in order to cause the formation to break down with the attendant formation of one or more fractures therein. Simultaneously with or subsequent to the formation of the fracture a suitable carrier fluid having suspended therein a propping agent such as sand or other particulate material is introduced into the fracture. The propping agent is deposited in the fracture and functions to hold the fracture open after the fluid pressure is released. The propped fracture provides larger flow channels through which an increased quantity of a hydrocarbon can flow, thereby increasing the production capabilities of a well.
A traditional fracturing technique utilizes a water or oil-based fluid to fracture a hydrocarbon-bearing formation. This technique is described in, for example, U.S. Pat. No. 3,858,658 to Strubhar et al.
Another successful fracturing technique has been that known as "foam fracturing". This process is described in, for example, U.S. Pat. No. 3,980,136 to R. A. Plummer et al. Briefly, that process involves generation of a foam which then is introduced through a wellbore into a formation which is to be fractured. Various gases and liquids can be used to create the foam, but foams generally used in the art are made from nitrogen and water in the presence of a suitable surfactant. The pressure at which the foam is pumped into the well is such that it will cause a fracture of the hydrocarbon-bearing formation. Additionally, the foam comes out of the well easily when the pressure is released from the wellhead, because the foam expands when the pressure is reduced.